The importance of antioxidant ingredients for skin health

Written by: Yuan Gao – Product Innovation Scientist at Lignopure

Antioxidant ingredients are essential for maintaining skin health due to their ability to protect against oxidative stress, which is a major contributor to skin aging and damage. The skin, as the body’s first line of defense, is constantly exposed to exogenous and endogenous oxidative conditions. Exogenous oxidative conditions arise from environmental pollutants such as smoke, smog, and UV radiation. Endogenous oxidative sources are a consequence of the body’s metabolic activity and diet. These external and internal factors lead to the formation of free radicals—unstable molecules that cause cellular damage by stealing electrons from healthy cells. This process, known as oxidative stress, can result in premature aging, hyperpigmentation, inflammation, and a compromised skin barrier. 

Antioxidants neutralize free radicals by donating electrons, thereby preventing the cascade of cellular damage. This protective action is crucial for preserving the skin’s structural proteins, such as collagen and elastin, which maintain skin’s firmness and elasticity. As a result, antioxidant ingredients are key in preventing and reducing the visible signs of aging, such as wrinkles, fine lines, and sagging skin [1]. 

Lignin, a powerful natural primary antioxidant

Antioxidants can be categorized based on their source in skincare. Natural antioxidants include vitamins like Vitamin C and E, plant extracts (e.g., green tea, resveratrol), and enzymes like superoxide dismutase. Synthetic antioxidants, such as butylated hydroxytoluene (BHT) and butylated hydroxyanisole (BHA), are lab-created for stability and efficacy in formulations. 

LignoBase, our lignin-based cosmetic ingredient line derived from natural sources, fits into the category of natural antioxidants. Plants are a rich source of biologically active compounds, with phenolic and polyphenolic substances standing out for their antioxidant properties. LignoBase is abundant in these phenolic and polyphenolic compounds. The antioxidant activity of these substances is largely determined by their chemical structure, particularly the number and positioning of hydroxyl groups and the presence of an aromatic ring. 

Mechanism of LignoBase’s antioxidant activity 

Antioxidants can be classified into primary and secondary types based on their mechanisms of action: 

1. Primary Antioxidants (also known as preventive antioxidants): These antioxidants directly neutralize free radicals by donating hydrogen atoms or electrons, thereby preventing the free radicals from causing cellular damage. Examples include Vitamin C, Vitamin E, and glutathione. They act immediately upon encountering free radicals, making them crucial in protecting skin cells from oxidative stress. 

1. Secondary Antioxidants (also known as repair or supportive antioxidants): These work indirectly by regenerating primary antioxidants, repairing oxidized molecules, or chelating metal ions that catalyze oxidative reactions. An example is Coenzyme Q10, which helps regenerate Vitamin E, allowing it to continue its antioxidant activity. Secondary antioxidants support the overall antioxidant network, enhancing skin protection and repair. 

LignoBase’s complex phenolic polymer contains numerous chemical functional groups, such as phenolic hydroxyl, carboxylic, carbonyl, and methoxyl groups that contribute to its antioxidant activity [2]. Like the commercial phenol-based antioxidants, the main functional group is still the phenolic hydroxyl group. The antioxidant effect of phenolic groups is primarily due to their ability to donate hydrogen atoms or electrons, which neutralizes free radicals and prevents oxidative damage. Therefore, LignoBase can be classified as primary antioxidants. Here’s how this mechanism works: 

1. Free Radical Scavenging: Phenolic compounds contain one or more hydroxyl groups (-OH) attached to an aromatic ring. These hydroxyl groups are highly reactive, enabling them to donate a hydrogen atom (H) to free radicals. This donation stabilizes the free radicals by pairing their unpaired electrons, thus neutralizing them and preventing them from causing further damage to cells. 

1. Resonance Stabilization: After donating a hydrogen atom, the phenolic compound becomes a phenoxyl radical. However, the aromatic ring structure of the phenol allows the unpaired electron in the phenoxyl radical to delocalize through resonance. This delocalization stabilizes the phenoxyl radical, making it less reactive and less likely to cause further oxidative damage [3,4]. 

LignoBase’s as an effective natural antioxidant  

In measurements of intracellular antioxidant activity in human keratinocytes (HaCaT), LignoBase demonstrated the capability to neutralize 70-98% of reactive oxygen species (ROS). In a basic facial cream formulation, all three variants of LignoBase enhanced antioxidant activity up to 43 times, increasing from 1.7% to at least 74%. (Experiment modified by Pan et al.’s model [5], which illustrates how lignin traps and stabilizes DPPH radicals, supports these findings.) Notably, even at a low concentration of 0.5%, LignoBase Cool boosted antioxidant ability by 64.49%, indicating its effectiveness at lower concentrations. Additionally, LignoBase has shown potential in stabilizing the photounstable UVA filter, Avobenzone. 

Overall, LignoBase’s natural origin, combined with its proven antioxidant and stabilizing properties, makes it an attractive and effective ingredient for improving skin health and longevity in cosmetic products. 

Reference 

[1] Ellsässer, S. Zusatzstoffe in Kosmetika. in Körperpflege und Kosmetik: Ein lehrbuch für die PTA-Ausbildung in der Apothekenpraxis 50–66 (2020). 

[2] Kabir, A. S., Yuan, Z.-S., Kuboki, T. & Xu, C. Development of Lignin-Based Antioxidants for Polymers. 39–59 (2019) doi:10.1007/978-981-13-3768-0_2. 

[3] Shahidi, F., & Ambigaipalan, P. Phenolics and polyphenolics in foods, beverages and spices: Antioxidant activity and health effects – A review. Journal of Functional Foods, 18, 820-897. (2015). 

[4] Rice-Evans, C., Miller, N. J., & Paganga, G. Antioxidant properties of phenolic compounds. Trends in Plant Science, 2(4), 152-159. (1997). 

[5] Li, S. X. et al. Preparation of organic acid lignin submicrometer particle as a natural broad-spectrum photo-protection agent. Int. J. Biol. Macromol. 132, 836–843 (2019).